What is the electric potential of the wire in a mains supply cable?
The electric potential of neutral wire in a mains supply cable is zero volts .
Explanation
Live (or, hot) wire carries electric current to the appliances.
Neutral wire is the normal "return" wire, that completes the circuit by forming a path for the current back to the mains. It is usually connected to ground (earth) near the transformer, and the earth is taken as zero potential. So, it maintains zero electric potential and functions as the return path for the current through the circuit.
Earth (or, ground) wire has very low resistance and is usually connected to the metal casing of the appliances. It forms a safety outlet for the current in case the appliance become live due to insulation breakdown within the appliance.
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